BS ISO 21909-2:2021 pdf free download – Passive neutron dosimetry systems Part 2: Methodology and criteria for the qualification of personal dosimetry systems in workplaces.
The location(s) at which the dosimetry system is qualified in the workplace shall be, at minimum, the one(s) representative for the usual locations of the workers in the room. In both approaches, it is acceptable to consider to characterizing the workplace field in terms of the energy dependence of the neutron fluence without taking into account the direction distribution of the neutron fluence (i.e., usual neutron spectrometers allowing the determination of H(10) can be used.)
6.2.2 Computational approach
The approach consists in using both:
— the information on the characteristics 01 the workplace in terms 01 energy and direction distributions of the neutron I luence from calculations. Apply the numerical approach described in (A2.2) to determine this information.
— and all the results of the tests of performance of the dosimetry system obtained from the type tests defined in ISO 21909-1. in order to qualify the dosimetry system at the workplace.
The dosemeters can be used at the workplace without corrections under the following conditions:
— a range of acceptable energy/angle responses against ISO 21909-1 shall be found by defining an upper and or lower energy limit; only mono-energetic beams demanded in ISO 21909-1 shall be considered for defining the limits;
— it shall be demonstrated by workplace calculations that 14(10) neutron dose contribution due to neutrons corresponding to energies/angles outside of the aforementioned defined range is lower than 10% of the total neutron dose.
The criteria given in ISO 21909-1 for the mono-energetic neutron fields shall be used to define the lower or upper limit in useful energy response of the dosimetry system.
6.2.3 ExperImental approach
The experimental approach is similar in concept to the computational approach but the dose contribution due to neutrons with energies below a threshold for low energies and/or above a threshold for high energies is assessed using experimental tool. Apply (A.2J.) to have the information on the energy distribution.
As stated previously, the workplace(s) in which the dosimetry system is to be qualified shall be the one(s) representative of the usual locations of the workers in the room.
6.3 Qualification based on experimental tests of the dosimetry systems at the workplace
To do this verification, a recalculation of all the doses measured for all the tests of Iso 21909-1, shall be done, considering the correction factor or function. It shall be demonstrated that the dosimetry system fulfils all the requirements of ISO 21909-1 (except the ones on the dependence of the response on energy and direction of incidence). For dosimetry systems using correction factor or function, a general verification can be performed before any workplace qualification considering all the potential correction factors or functions routinely used by the IMS.
NOTE To illustrate the importance of doing this verification, consider the case of the tests for effects on unexposed dosemeters required by ISO 21909-1. To be more precise, the example of the test described in ISO 21909-1:2021. 8.3, which deals with the effect of storage for unexposed dosemeters, can be considered. Indeed, if a correction factor is applied after the qualification at the workplace, the result of this test can change and the criteria can be not fulfilled anymore. Before applying the correction factor or function, such a test would be fulfilled, but after the application of the correction factor or function, the test criteria would not be met any more.
6.3.6 Unique correction for several workplaces
This subclause addresses the specific case where the same dosemeter is worn by a worker at different workplaces. In that case, one unique correction factor or function should be used for all the considered workplaces.
A qualification shall be performed at each workplace. For each workplace, the most appropriate method for qualifying the dosimetry system shall be used. For instance, the choice is partly determined by the dose equivalent rate of each workplace. The methods are described in 6.3.
For each workplace, a correction factor or function is defined (if needed). But in order for the dosimetry system to be used by a worker at all these different workplaces, the applied correction factor or function on the dose reading is necessarily unique. As a consequence, one unique correction factor or function needs to be defined.